1. Field of the Invention
The present invention is related to a restraint system for loading air cargo along a centerline of a cargo hold.
2. Background
Commercial aircraft carry cargo in containers and pallets, referred to collectively as unit load devices (ULDs). ULDs are available in several different standard configurations with different lengths and widths. During loading and unloading operations, ULDs must be guided within the cargo compartment. During flight, ULDs must be retained to prevent damage to the aircraft and the cargo. Floor-mounted devices, such as guides and restraints are typically used for these purposes and some such devices (referred to herein as a “guide/restraint”) serve both functions.
The deck of a Boeing 747 main cargo compartment is configured with a multitude of longitudinally extending retaining devices such as seat tracks (sometimes referred to as “seat rails”) and lock trays to which such guides, restraints and guide/restraints (collectively, “conveying devices”) are attached. A number of these retaining devices and conveying devices are positioned to accommodate some containers in predetermined locations in a side-by-side configuration along the centerline of the 747 main cargo deck.
From time to time, a 747 main cargo compartment must carry out-sized cargo (i.e., cargo that does not fit in standard positions because it would interfere with the inside contour of a cargo hold). An example of out-sized cargo might be a large turbine engine which, due to its large width and circular profile, cannot be loaded in a standard location close to the cargo hold sidewall. In such case, the out-sized cargo is loaded onto a standard-size pallet which in then placed along the centerline of the cargo hold. Currently, standard-sized pallets for air cargo transport are approximately 96 inches wide and either 20 feet, 16 feet or 10 feet in length. Mounting such a pallet along the centerline results in the long sides of a pallet extending about 48 inches on either side of the centerline.
Currently, the 747 cargo deck is not equipped with guide/restraints that are suitable for both guiding containers and retaining centerline mounted pallets. As a result, on a 747 main cargo deck, a centerline loaded pallet is normally tied down using straps. This method of restraining the pallet requires a large amount of manpower, requiring a number of personnel trained to properly strap cargo securely. It also delays the unloading of the such cargo, due to the time it takes to safely remove the straps at the destination.